This invention relates to the incineration of waste products such as rice and peanut hulls and the control of its ash residue.
The disposal of low value by-products from the processing of agricultural food crops, generally involves the burning of such by-products which creates many problems for the food producing industry. By-products such as rice and peanut hulls, for example, are tough, woody and abrasive. Further, such waste products are large in bulk, variable in density and have high ash and silica content. Incineration of such hulls is expensive, consumes large quantities of energy and creates air pollution problems.
The controlled combustion of the foregoing type of waste products has heretofore been attempted with little success from either an economic standpoint or from an ecological standpoint. Because of feed density variation, overfiring or underfiring often occurs during combustion resulting in unstable heat generation and exhaust gas quality that is not satisfactory for heat recovery purposes. For example, the introduction of waste products with high ash and silica content into the combustion chamber of a burner, generates an exhaust stream with excessive fly ash causing damage to and deterioration of boiler tubes because of silica related abrasiveness. Prior burners are also unable to control the degree of burn and therefore lack flexibility for control of the ash content of the combustion residue as a marketable product.
It is therefore an important object to provide an economical combustion system for low value waste products such as rice hulls that does not require pre-feed treatment or prior expensive processing of the waste product and accommodates wide variations in its bulk density occurring either naturally or from packaging or pelletizing for transport purposes.
Another object is to provide a combustion system for such low value waste products whereby the ash content of the combustion residue may be controlled and the fly ash content of its gaseous exhaust minimized.